Below are some examples of

Question: What was the first use of spacecraft thermal control louvers, doors, pinwheels, or other things that physically actuate either passively or actively?

From this answer to What are the louver-like structures on the sides of the Mariner 4 probe?

I just ran across the louvers in close-up view!

In the JLP video 1965: Discovery at Mars there is an excellent video The Changing Face of Mars with introductory remarks by its producer/director/writer, Blaine Baggett, Director, Office of Communication and Education, JPL, about Mariner 3 and 4 missions to Mars embedded within his Von Karman lecture.

At about 00:38:50 you can see them "moving" (could be Mariner 3 or 4):

Mariner 4 thermal louvers

From What are these air-vent-like structures on this satellite?

I struck out with my previous question so I'll try again.

What are these large circular 4-vane structures on the sides of NOAA-19 - the satellite that "fell down"?

They remind me of adjustable air vents but I have a feeling that's not quite right.

You can see them from another angle here.

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Spacecraft rotated for better view:

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1 Answer 1


Partial as i cannot currently find something that states "first":

But i note that:

Vanguard, Explorer, Pioneer, and previous Sputniks had passive thermal protection only (if any).

By May 1958, that leaves the Soviet Sputnik 3.


A fan circulated the internal nitrogen atmosphere of the satellite and 16 external louvers would open and close as needed to help maintain the internal temperature.

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If Object D (same design as Sputnik 3, latter being the back up) had had a successful launch then it would have been the first in April 1958.

  • 1
    $\begingroup$ I am always amazed that the Soviets kept their electronics pressurized with a little fan to blow the air around and keep things cool. So typically Soviet! Simple, brute force, rugged. $\endgroup$ Feb 1, 2022 at 20:12

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